One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,4)(6,9)(10,12)(13,14)(15,24)(16,20)(17,22)(18,23)(19,27)(21,26)(25,28) involution — undirected(5,6)(7,10)(8,9)(11,12)(13,15,17,26,18,16,19,25)(14,20,22,28,23,24,27,21)(5,7,8,11)(6,10,9,12)(13,16)(14,21)(15,18)(17,26)(19,25)(20,27)(22,24)(23,28)(2,4)(6,9)(10,12)(13,17,18,19)(14,22,23,27)(15,25,16,26)(20,21,24,28)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.